| Noun | 1. | Adiantum - cosmopolitan genus of ferns: maidenhair ferns; in some classification systems placed in family Polypodiaceae or Adiantaceaefern genus - genera of ferns and fern allies family Pteridaceae, Pteridaceae - one of a number of families into which the family Polypodiaceae has been subdivided in some classification systems; Pteridaceae is itself in turn sometimes further subdivided maidenhair, maidenhair fern - any of various small to large terrestrial ferns of the genus Adiantum having delicate palmately branched fronds |